Effects of Quiet Eye Training on Performance of Bimanual Coordination in Children with DCD

Objectives Children with developmental coordination disorder (DCD) are physically characterized by poor motor coordination and are at particular risk of losing their motor control. Quiet eye training (QET), with the latest techniques as an uncomplicated approach recently entered the field of rehabilitation research, has drawn the researchers’ attention. Therefore, the objective of this study was to examine the effects of QET on the performance of bimanual coordination in children with DCD. Materials & Methods Children with DCD (n=20; aged 8-9 years) were randomly divided into two groups, including QET and traditional training (TT). The participants performed bimanual in-phase and anti-phase movements with their wrists at three speed levels ranging from slow to fast. Bimanual coordination accuracy was assessed at the baseline, after 4 weeks at study completion, and at the retention test. Results Bimanual coordination improved over time from the baseline to study completion. The results showed that there was a significant difference between the pretest and posttest in the QET group (P=0.001), and bimanual coordination accuracy in the posttest significantly increased, compared to that reported for the pretest. Moreover, there was a significant difference between the pretest and posttest in bimanual coordination accuracy in the TT group (P=0.01), and the posttest accuracy significantly increased (F=2.32); however, the increase was less than that of the QET group. Conclusion The obtained results indicated that the performance of the in-phase and anti-phase coordination modes was strongly influenced by QET. Furthermore, it was concluded that a successful performance of a bimanual linear task mainly depends on the availability of visual feedback.


Introduction
Motor development is the process in which children suffuse movement patterns and motor skills (1).
Normal childhood development follows a fairly predictable pattern; however, it sometimes causes problems created in the process of children's motor development (2, 3). One of the disorders that affect motor coordination, gross motor skills, and fine motor skills is developmental coordination disorder (DCD). The condition is characterized by a poor performance of motor skills that has a significant and negative impact on daily activities (4). The DCD is used to describe children without neurological disorders or medical problems, particularly problems affecting academic and social functions (5).
Studies related to children with DCD have shown that the use of various intervention programs has been noted in recent years. Zwicker et al. (2015) have shown that orientation tasks as an essential component of many interventions should be particularly regarded (6). Niemeijer et al. showed that motor function did not improve in children; nevertheless, intervention (i.e., physiotherapy exercises) has been effective (7). Over the past few years, the physiotherapy approach and occupational therapy of patients have evolved from traditional

Conclusion
The obtained results indicated that the performance of the in-phase and anti-phase coordination modes was strongly influenced by QET.
Furthermore, it was concluded that a successful performance of a bimanual linear task mainly depends on the availability of visual feedback. The quiet eye (QE) was defined by Vickers (11) as the final fixation or tracking gaze on an object (for >100 MS to within 3° of visual angle) before the onset of a critical movement and has been observed to be a key predictor of perceptual-cognitive skill in a wide range of movement tasks. The QE has been shown to be a trainable key marker of proficient motor performance (10). The QET aims to help performers adopt the QE of a highly skilled prototype (10, 11). The initial studies of QET in the sporting domain have been successful in accelerating the novice performers' skill acquisition, compared to traditional training (TT) (12). In this regard, Miles et al. (2014)  However, in the aforementioned study, the effect of QET has not been investigated (9).

Keywords
Numerous daily life activities require continuous updating of the perception-action cycle to maintain the accuracy of human motor behavior (15).
Among the different sensory modalities, vision has been identified to be essential for planning and guiding movements in time and space (16).
For upper limb movements, the principles of coordination are realized in two stable patterns, namely in-phase (i.e., 0 0 relative phases) and anti-phase (i.e., 180 0 relative phase) (17)(18)(19). The in-phase coordination mode refers to mirrorsymmetrical movements simultaneously made toward and away from the body midline (17,20,21). The anti-phase coordination mode refers to movements simultaneously made in the same direction from one side of the body midline to its different side, resulting in the performance of a parallel movement pattern in extrinsic space (20,22,23).
At least for perceiving spatial information, vision dominates other senses (24). Many motor tasks are impossible or, at least, are much harder to perform without vision, such as walking on uneven terrain, hitting a tennis ball, or skiing (21,24). Confirmed evidence that vision plays a critical role in the coupling of limb movements came from studies using both discrete (25) and cyclical bimanual movements (26). Specifically, these studies have shown that bimanual coordination movements were performed with higher levels of accuracy when visual information on the position of moving effectors was available, compared to those of other conditions where visual feedback was absent (27,28).
It is well established that predictive eye movements support the planning and controlling of goaldirected movements in natural environments (29). Furthermore, gaze behavior differentiates between children with and without DCD (30,31).
Accordingly, there are many QE discoveries yet to be made regarding motor tasks and for patients with disabilities and requiring rehabilitation (11). The gaze registration techniques provide an insight into how external visual information is used to guide and control goal-directed motor actions (30). Studies have shown that children with impaired motor coordination use less effective gaze strategies in controlled laboratory reaction time (32), visual tracking (30), and reach-to-grasp (33) tasks. Therefore, the current study aimed to examine the impacts of QET on the performance of bimanual coordination in children with DCD.

Materials & Methods
The participants were chosen based on the MABC test and were 20 elementary school children with DCD comprised of males aged 8 to 9 in Urmia, Iran. where ɸR is the phase of the right wrist at each sample; XR is the position of the right wrist rescaled to the interval, {-1, 1} for each cycle of oscillation; (dXR/dt) is its normalized instantaneous velocity.
The same formula was used to calculate the position and velocity signals of the left wrist. The relative phase (ψ) between the two wrists was then declared as follows: The participants were randomly divided into two groups after the pretest (i.e., TT and QET group).
After the pretest, all the participants in both

Results
There were no differences between the TT and    Overall, this finding revealed that when the children with DCD used QET, they performed both the inphase and anti-phase coordination tasks with lower   a motor action but with anticipating its sensory consequences.
The important implication of this approach is that all the constraints of motor control, such as complexity effects, stimulus-response compatibility, and/or symmetry tendencies, in bimanual coordination do not arise due to constraints inherent in the structure and/or functions of the motor system, but due to constraints in the representation of the perceptual re-afferences of to-be-produced motor actions (41). More studies should be conducted to further examine this hypothesis.

In Conclusion
The findings suggest that in children with DCD, QET